Harvesting: manual or mechanical?
The grape harvest in Italy is mainly carried out by hand: it must be applied in the case of some Dorigine denominations, in the case of certain cru or in the vineyards where noble rot is sought. In general, the manual harvest allows to obtain a product qualitatively superior to the mechanical harvest: the grapes are harvested intact (it is not crushed and the berries are not broken), the berries or the bunches compromised by diseases or other are eliminated, the vegetable residues are eliminated which can end up in the collection boxes, can be harvested certain cru or varieties present in the same vineyard separately or, even, a scalar harvest of a single variety can be made.
In the last thirty to forty years, however, there has been an increase in the use of grape harvesting machines, either because of the increase in production costs, or because of the decrease in available labor. In general, the mechanical harvest has obvious advantages in terms of the time taken to carry out the harvesting operations (0.3-0.5 hours / ha against the 300 hours / ha of the manual harvest); however, the qualitative characteristics of the harvested grapes are clearly inferior to the harvested grapes with manual harvest: the qualitative potential of the grapes is standardized downwards, which is tolerable for table wines, but not for quality wines.
In the context of Italian viticulture, in general, there are various problems that do not facilitate a wider spread of the mechanical harvest, in particular viticultural obstacles and oenological difficulties:
- viticultural obstacles: there are innumerable viticultural obstacles to the spread of the mechanical harvest in Italy: pulverization of the plots and small dimensions of the same (lack of spaces at the headland for the maneuvers of the machine); existence of terraces and terraces; height and type of poles (must be wooden); breeding forms that do not adapt to the grape harvesting machine; presence of vines with berries sensitive to breakage and which lose must during shaking, etc .;
- oenological difficulties: unlike the manual harvest, the mechanical harvest brings broken berries to the cellar, often without stalks, with, sometimes, a considerable percentage of must (7-15%); for these reasons, this practice cannot be adapted to the production of sparkling wines, holy and fortified wines, which require particular harvests and appropriate harvest choices. The mechanical harvest leads to qualitative homogenization, appropriate for mass products. Other negative aspects of the mechanical harvest under the oenological aspect are an increase in the herbaceous aroma and bitter taste; the duration of aging is reduced; the must produced by breaking the berries during the harvest undergoes enzymatic oxidation phenomena, which cannot be stopped in the cellar; mechanical removal of leaves, petioles, bark, residues from the palisade is difficult, which can compromise the presses and pumps in the cellar.
Finally, the economic aspects of the mechanical harvest must be considered: its cost can be up to two-three times lower than the manual harvest. Obviously, the specific cost varies depending on the region, depending on whether the machine is purchased by the individual winemaker or is rented, depending on the area under vines. Finally, it would be interesting to add to the costs of the mechanical harvest also the costs incurred to make the vineyard subject to it.
Self-propelled horizontal shaker grape harvester (Grape harvesters)
Transport operations must be considered in the overall collection site, as they are necessary for the harvest-cellar connection: it is advisable to carefully evaluate both the oenological and economic aspects.
From the point of view of the oenological aspect, the transport must not compromise the integrity of the grapes and safeguard their physical and biochemical state which they present at harvest, up to the transfer into a receiving container. Obviously the state of the grapes after the harvest depends mainly on the type of harvest carried out: if manual, the grapes are certainly more intact and their manual handling also allows greater care in the cellar; if mechanical, the grape is de-stemmed, partially crushed, overloaded with vegetable residues (leaves, bark, etc.). The transport operations following manual or mechanical harvesting are therefore different: following mechanical harvesting it is necessary to quickly start the grapes at the cellar, after having separated the juice from the solid parts as much as possible, to preserve its characteristics as much as possible.
From an economic point of view, the mechanical harvest guarantees advantages in terms of time and quantity also for transport: a greater quantity of grapes transported to the cellar (4-10 t / hour), with a duration of the harvest that can last up to 12 hours a day.
Cleaning and sorting of the grapes
The cleaning and sorting of the grapes consists in the removal of both unwanted plant residues (leaves, branches, etc.) and grapes in bad conditions, moldy or not sufficiently ripe.
Both in the case of manual and mechanical harvesting, in general, at least for red grapes, the elimination of vegetable residues is carried out at the same time as destemming and pressing. Remembering that the grapes from the two types of harvest mentioned above are very different, for what concerns the mechanical harvest it would be appropriate to use the most suitable systems for cleaning the grapes, which surely, in the near future, will be studied and applied.
Sorting the grapes to eliminate those in bad condition is particularly effective on whole grapes derived from manual harvesting and can also be done when filling the trailers for transport, in order to facilitate operations in the cellar. The same sorting is not very effective, however, for grapes harvested by machine; if necessary, a removal of the moldy or insufficiently mature bunches in the pre-harvest can be carried out, by employing staff who carry out the operation before the passage of the grape harvester.
Manual cleaning and sorting of the grapes (source www.vitevinoqualita.it)